William Melstrom on wed 22 sep 04
David -- your slip contains organic materials that are decomposing. I
recently wrote two long messages pertaining to spoilage of glazes on a
crystalline glaze message board. Not all of the info is specifically
pertinent to your situation, but here are the messages:
I have been amazed at the responses to the "shelf life of glazes" thread. I
mix up either 5,000-gram batches of WET glaze, or, occasionally 10,000 gram
WET batches. These will fill a PLASTIC bucket either halfway or all the way
full. It might be as long as TWO YEARS sometimes even longer, before I use
all of a glaze.
I never have problems with glaze degradation.
It is well known that CMC spoils over time. This is easy to demonstrate for
yourself - just mix a little with plenty of water in a clear glass jar, and
see what happens. Within two weeks, you should begin to see black mold
growing in the solution. The mold will grow much quicker in warmer
conditions. CMC is an organic material, not an inorganic mineral, and as
such, is therefore prone to spoilage. Many glaze components, which are
basically just raw mined materials, also contain small amounts of organic
materials, particularly clays and feldspars. These glaze materials will also
spoil, but not nearly as much as CMC, due to their only containing trace
amounts of organic material.
I have found that spoiled crystalline glazes are completely useless.
I use what I consider to be an unusually high percentage of CMC in my
crystalline glazes. I add formaldehyde, purchased as a 37% solution, to
prevent spoilage. I add about an ounce to 2 ½ gallons (half a bucket) of
mixed glaze. I don't measure. If I think the glaze might be sitting around
for a really long time, I add a little extra.
I am not recommending that anyone else use formaldehyde. Formaldehyde is
extremely nasty, and you need to ask yourself some serious questions before
you decide to use it.
I have been using formaldehyde for over ten years, and every time I buy it,
it becomes harder to find. I have never used the same source twice, because
each source stops dealing in it. It is still out there, however, but I don't
know how regulated it is. The last time I bought some, I got a whole gallon,
not knowing how difficult it would be to find next time. A gallon is a lot.
I know of no substitute for formaldehyde. I have heard anecdotal reports of
people unsuccessfully trying chlorine. The only other alternative that I
know of is to refrigerate your glaze. I have never tried this, but I have it
on very good authority that this works.
I also add an unusually high percentage of bentonite to my glazes. Combined
with the CMC, it means that my glazes pretty much never settle. Combined
with the effects of the formaldehyde, perhaps this is why my glazes do not
clump, crystallize in the bucket, react with the plastic or themselves, or
become soluble.
The second message:
Yes, formaldehyde, really.
Honestly, it doesn't smell that much. I think that you must have been
smelling the frog and the shark.
The real issue is one of health. I did a little internet research a while
back, all the sources I found made formaldehyde sound worse than lead, while
at the same time being pretty vague and non-specific. If any one has any
factual info regarding problems with formaldehyde, I would like to know of
it.
I do know that formaldehyde is all around us. It is used in lots of
construction materials such as drywall, wallpaper, carpet, finishes and
adhesives. Very sensitive people have to avoid entering new constructions
because of the formaldehyde and other released chemicals.
I also know from personal experience that formaldehyde will give you a
headache and leave you fatigued the day after using it. After realizing what
was going on, I changed my processes, and this is no longer a problem.
Formaldehyde is abused on the street. A cigarette dipped in formaldehyde is
called a "wet." I believe that the formaldehyde is just flammable enough to
keep the "wet" lit. We're talking really serious self-abuse here, worse than
huffing.
I wonder about what is in those little jars of pre-mixed Amoco and Duncan
glazes. I am certain that they must contain gum because they brush on so
smoothly. If so, I wonder what they use to prevent spoiling.
When my brother was a teenager, many years ago, he suffered from
hyper-hydrosis of his hands. I think it was mostly in his head, but he was
really hung up on it, imagining that it would interfere with dating. My
parents took him to a dermatologist, and the prescribed therapy was to soak
his hands in formaldehyde for 30 minutes every day! When I first began using
formaldehyde in my glazes some 10 years ago, the smell, which I hadn't
experienced in some 20 years, instantly brought back the memory of my
brother soaking his hands. I'd love to hear what a M.D. today would think of
this.
As for the potters of old, I first learned about using formaldehyde from one
of the early editions of Chappell's infamous "Clay and Glazes for the
Potter" which was in my University's library. I say infamous, because none
of the glazes worked right. Chappell added .5% of CMC to almost every one of
his glazes, along with a "couple of drops" of formaldehyde to prevent mold.
It is still a popular book, and I wonder if the fairly recent current
addition still advocates using formaldehyde.
Keeping your mixed gums in the refrigerator is a good solution. I don't know
where you learned to do this, but you're way ahead of most people in this
regard.
In my personal experience, I have not observed copper inhibiting bacteria
growth, but I could be wrong.
I am very interested to know what Steven Hill is using to prevent bacteria.
Using anything at all sounds somewhat counter-productive - bacteria in clay
increases plasticity. However, I have smelled really bad clay, and it can be
pretty overpowering.
I would be lost without formaldehyde or an equally effective substitute. Not
having it would require such a change in my processes, that I would probably
stop doing crystalline glazes altogether.
William Melstrom
Austin, Texas
www.handspiral.com
Howdy kind folks,
ANybody have an idea why my slip is growing mold a few days after I've
mixed it? it's dark grey and stinks like hell. It was white and creamy.
Is there an additive that controls this?
thanks so much
David
Brooklyn
Wayne on thu 23 sep 04
William:
Formaldehyde is still available in both a 10% and 37% solution.
Directly from Globalspec.com (a great industrial search engine, by
the way...(and no connection)), we find:
SPI-Chem Formaldehyde 37%, EM Grade - SPI Supplies=20
...SPI-CHEM=99 Formaldehyde.. Formaldehyde solution, 37% CH2O..
Appearance: Clear, colorless liquid.. Odor: Pungent odor..=20
http://www.2spi.com/catalog/chem/chem2a1.shtm... - (cached)=20
See Structure Probe, Inc. Information=20
=20
Formalin, Formaldehyde, 10% Buffered Solution, 18510, MSDS=20
...FORMALDEHYDE: Acids (inorganic): Formaldehyde solutions react.
Alkalies (strong): Formaldehyde solutions react. Ammonia:
Incompatible. Anhydrides: Formaldehyde solutions react..=20
http://www.tedpella.com/msds_html/18510msd.ht... - (cached)=20
See Ted Pella, Inc. Information=20
=20
D.B. Western, Inc. Home=20
...Formaldehyde,hcho,ufc,resin,urea,melamine,chemical
engineering,HCHO,UFC,dbwestern, db western..=20
http://www.dbwestern.com/ - (cached)=20
See D.B. Western, Inc. Information =20
I don't use it personally. =20
Hope that helps,
Wayne Seidl
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of William
Melstrom
Sent: Wednesday, September 22, 2004 11:36 PM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: mold in slip (LONG)
I add formaldehyde, purchased as a 37% solution, to
prevent spoilage. I add about an ounce to 2 =BD gallons (half a
bucket) of
mixed glaze. I don't measure. If I think the glaze might be sitting
around
for a really long time, I add a little extra.
I am not recommending that anyone else use formaldehyde.
Formaldehyde is
extremely nasty, and you need to ask yourself some serious questions
before
you decide to use it.
I have been using formaldehyde for over ten years, and every time I
buy it,
it becomes harder to find. I have never used the same source twice,
because
each source stops dealing in it. It is still out there, however, but
I don't
know how regulated it is. The last time I bought some, I got a whole
gallon,
not knowing how difficult it would be to find next time. A gallon is
a lot.
I know of no substitute for formaldehyde. I have heard anecdotal
reports of
people unsuccessfully trying chlorine. The only other alternative
that I
know of is to refrigerate your glaze. I have never tried this, but I
have it
on very good authority that this works.
William Melstrom
Austin, Texas
www.handspiral.com
Jim Pendley on thu 23 sep 04
Formaldehyde and derivatives are suspected or
anticipated human carcinogens. The fumes also can
" fix" as in "preserve" the corneas of the eyes
requiring transpants. So use should be extremely
careful, especially in venting. Carolina Scientific
sells "Carosafe" with is mainly gycol solutions as
a safer substitute. It also contains a very very small
amount of formaldehyde but is much safer. Also one
might use some of the perservatives that are used in
food preservation ( usually acids), but I do not know
how this would affect the clay materials. In the
College where I taught in biological sciences, we
eventually bought a very large refrigerator to store
the partially dissected materials because once the
material was removed from the original bag, it was
only
a matter of time before "fuzzy" things would grow. I
recommend a refrigerator also, but obviously not the
same one as the family's :)
Jim Pendley
--- Wayne wrote:
> William:
> Formaldehyde is still available in both a 10% and
> 37% solution.
> Directly from Globalspec.com (a great industrial
> search engine, by
> the way...(and no connection)), we find:
>
> SPI-Chem Formaldehyde 37%, EM Grade - SPI Supplies
> ...SPI-CHEM™ Formaldehyde.. Formaldehyde solution,
> 37% CH2O..
> Appearance: Clear, colorless liquid.. Odor: Pungent
> odor..
> http://www.2spi.com/catalog/chem/chem2a1.shtm... -
> (cached)
> See Structure Probe, Inc. Information
>
> Formalin, Formaldehyde, 10% Buffered Solution,
> 18510, MSDS
> ...FORMALDEHYDE: Acids (inorganic): Formaldehyde
> solutions react.
> Alkalies (strong): Formaldehyde solutions react.
> Ammonia:
> Incompatible. Anhydrides: Formaldehyde solutions
> react..
> http://www.tedpella.com/msds_html/18510msd.ht... -
> (cached)
> See Ted Pella, Inc. Information
>
> D.B. Western, Inc. Home
>
...Formaldehyde,hcho,ufc,resin,urea,melamine,chemical
> engineering,HCHO,UFC,dbwestern, db western..
> http://www.dbwestern.com/ - (cached)
> See D.B. Western, Inc. Information
>
> I don't use it personally.
> Hope that helps,
> Wayne Seidl
>
> -----Original Message-----
> From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On
> Behalf Of William
> Melstrom
> Sent: Wednesday, September 22, 2004 11:36 PM
> To: CLAYART@LSV.CERAMICS.ORG
> Subject: Re: mold in slip (LONG)
>
> I add formaldehyde, purchased as a 37% solution, to
> prevent spoilage. I add about an ounce to 2 ½
> gallons (half a
> bucket) of
> mixed glaze. I don't measure. If I think the glaze
> might be sitting
> around
> for a really long time, I add a little extra.
> I am not recommending that anyone else use
> formaldehyde.
> Formaldehyde is
> extremely nasty, and you need to ask yourself some
> serious questions
> before
> you decide to use it.
> I have been using formaldehyde for over ten years,
> and every time I
> buy it,
> it becomes harder to find. I have never used the
> same source twice,
> because
> each source stops dealing in it. It is still out
> there, however, but
> I don't
> know how regulated it is. The last time I bought
> some, I got a whole
> gallon,
>
Ron Roy on fri 24 sep 04
Hi William,
Some info from Monona's book - The Artists Complete Health and Safety Guide.
Formaldehyde - Air quality limits 0.3 ppm TLV-C
Formaldehide is a sensitizer and a suspect carcinogen.
Looks like you should try to limit your exposure as much as possible.
RR
>The real issue is one of health. I did a little internet research a while
>back, all the sources I found made formaldehyde sound worse than lead, while
>at the same time being pretty vague and non-specific. If any one has any
>factual info regarding problems with formaldehyde, I would like to know of
>it.
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Bonnie Staffel on fri 24 sep 04
I am wondering whether CMC is the cause of the mold in your glazes or if
some ingredient in your glaze is having a causative effect. I have said
before on Clayart that I have never had mold develop in my glazes. I use
very hot water when I mix my glazes and also thinking if you use ball clay,
there might be some contaminant in that. I use Kaolin. I really think that
something else could be the culprit. I also have had CMC mixed and put into
jars, still no mold. I found the following information on the Internet.
They use CMC in toothpaste and food products. I am sure that mold formation
would keep it out of such materials. There are several different grades,
perhaps you have the wrong grade for ceramic use. I have had studios in
northern Michigan, western North Carolina and Mississippi. In none of those
places have I had any problem with mold. Actually, in my glazes CMC acts as
a deflocculant so that less water is needed to get the right coat on my
bisque from dipping. My glaze does not powder and takes my decorating
techniques very well.
"Depending on time, temperature, pH, gum can be attacked by microbes or
molds. If this happens store in a cooler place, make smaller batches, adjust
the pH to make a less friendly environment, or add an antiseptic (i.e.
NaN3). Many brush on glazes use CMC and can have a shelf life for this
reason.
"If you want more information or if you have any questions regarding CMC
please contact haggis.matray@AkzoNobel.com "
Warm regards,
Bonnie Staffel
http://webpages.charter.net/bstaffel
http://www.vasefinder.com/
Potters Council member
William Melstrom on fri 24 sep 04
Bonnie:
Your post is interesting.
Your experiences with CMC definitely differ from mine. I have placed about
a teaspoon of CMC in a glass jar with plenty of water and a plastic lid. I
shake it every so often for a couple of days until it completely dissolves.
In less than a week, there is black fuzzy mold suspended in the solution. I
am using food grade CMC. I've done this test more than once, always with
the same result. I'll do it again right now, and post a link to a photo of
the result.
I might note that I live in Texas where it is warm, and I have no means to
refrigreate 5 gallon buckets of glaze.
Yours,
William Melstrom
www.handspiral.com
> I am wondering whether CMC is the cause of the mold in your glazes or if
> some ingredient in your glaze is having a causative effect. I have said
> before on Clayart that I have never had mold develop in my glazes. I use
> very hot water when I mix my glazes and also thinking if you use ball
clay,
> there might be some contaminant in that. I use Kaolin. I really think
that
> something else could be the culprit. I also have had CMC mixed and put
into
> jars, still no mold. I found the following information on the Internet.
> They use CMC in toothpaste and food products. I am sure that mold
formation
> would keep it out of such materials. There are several different grades,
> perhaps you have the wrong grade for ceramic use. I have had studios in
> northern Michigan, western North Carolina and Mississippi. In none of
those
> places have I had any problem with mold. Actually, in my glazes CMC acts
as
> a deflocculant so that less water is needed to get the right coat on my
> bisque from dipping. My glaze does not powder and takes my decorating
> techniques very well.
>
> "Depending on time, temperature, pH, gum can be attacked by microbes or
> molds. If this happens store in a cooler place, make smaller batches,
adjust
> the pH to make a less friendly environment, or add an antiseptic (i.e.
> NaN3). Many brush on glazes use CMC and can have a shelf life for this
> reason.
>
> "If you want more information or if you have any questions regarding CMC
> please contact haggis.matray@AkzoNobel.com "
>
> Warm regards,
>
> Bonnie Staffel
Bonnie Staffel on sat 25 sep 04
Dear William,
I truly believe you. As for the use of the CMC I have, I purchased it so
long ago that I do not know what grade it is. I purchased it from a pottery
supplier, however, so figure it was made for use with glazes.
I note that you just put it in cold water. Have you tried using boiling
water in a blender, adding the small amount of CMC so that it dissolves
almost immediately. This is how I make mine. Perhaps the boiling of the
water kills some of the microbes. Try it and see if your test still is the
same. However, when mixing my very large amount of glaze, I still use very
hot water from the tap and dry blend the CMC with some other material so
that it disperses right away. My glaze seems to be ready for use by the
next day. Still no mold ever with my method.
Regards,
Bonnie Staffel
| |
|
